It has long been known to pump water or compress air using a device relying on alternatingly admitting air and water into a coiled pipe, which is rotated around an axis of rotation. Such a device has few moving parts, and is considered to be relatively simple and reliable.
For instance, GB 1 427 723 discloses an apparatus for pumping fluids, which comprises a pipe of constant cross-section disposed around a cylindrical structure in a number of turns so as to form a cylindrically shaped coil. One end of the coiled pipe is connected to a hollow shaft of the apparatus, while the other end of the coiled pipe terminates at the periphery of the cylindrical structure and is open to the atmosphere. When the cylindrical structure is rotated, water and air are alternatingly admitted to the open end of the pipe and transported to the hollow shaft.
Although the apparatus according to GB 1 427 723 is capable of pumping water and compressing air, there appears to still be room for improvement. In particular, it would be desirable to provide a more energy-efficient apparatus for converting rotation into fluid flow and/or converting fluid flow into rotation.